Extend button on Electric Eel doesn't open the Extend window

When I open Manage Devices of my pool, select my RAIDz3 and click Extend, the screen get a little darker, but the Extend window doesn’t open.

I see in the browser console log:
error-handler.service.ts:38 TypeError: Cannot read properties of undefined (reading ‘size’)
at raidz-extend-dialog.component.ts:90:19
at Array.reduce ()
at pe.setFilterMinimumSizeFn (raidz-extend-dialog.component.ts:88:49)
at new pe (raidz-extend-dialog.component.ts:54:10)
at pe.ɵfac [as factory] (raidz-extend-dialog.component.ts:94:3)
at me.onRaidzExtend (zfs-info-card.component.ts:214:20)
at zfs-info-card.component.html:68:87

Just wanted to say I’m having the same issue as of a few days ago.
It appears for me when when expanding my VDEV (mine is RAIDz2).

I’ve also had an issue with duplicated disks, which I suspect could be causing the issues. For example the serial number of sdf is the same as sdk. I have only 9 physical disks in my system, but TrueNAS shows me as having 14 drives.

The issue I was facing with duplicated disks appears to be an issue with multipathing - an unsupported (or improperly configured) feature in the version of TrueNAS I’m using. Or perhaps is my DAS or HBA. Regardless, it was causing some issues for me but that’s resolved now.

Once I resolved my other issues, this issue with the API went away for me.
@TommyAtKadx I dunno if your issue is the same as mine, but the symptoms were identical. Worth looking into anyway.